In known cases of this type, the unlocking of the catch means leaves the cover practically closed on the base, so that the user must open it, for example by inserting a fingernail into the free space between the base and the cover. Moreover, the cover tends to return to the closed position by gravity, which militates against a rational use of the case.
To overcome this drawback, it is known to arrange a return spring, for example a helicoidal spring wound about the articulation axle and whose ends bear respectively on the base and the cover. The mounting of such a spring is complicated and difficult for cases of small dimensions such as compacts. Moreover, the return force is difficult to calibrate so as not to provoke a too abrupt and/or too complete opening.